Patent application title: REAR-PROJECTION DISPLAY

Abstract:

Various embodiments related to rear-projection image display are
disclosed. For example, one disclosed embodiment provides a projector for
projecting an image and a screen configured to display the image. The
screen comprises a filter layer having a light reception side and an
image display side. The filter layer includes an array of trapezoidal
transmissive elements and an array of trapezoidal absorption elements,
where a wider base of each of the trapezoidal transmissive elements faces
the light reception side of the filter layer, and where a wider base of
each of the trapezoidal absorption elements faces the image display side
of the filer layer.

Claims:

1. A rear-projection display device for displaying an image, comprising:
a projector configured to project an image; and a screen configured to
display an image projected by the projector, the screen including a
filter layer comprising a light reception side and an image display side,
the filter layer further comprising an array of trapezoidal transmissive
elements with a wider base of each trapezoidal transmissive element
facing the light reception side of the filter layer, and an array of
trapezoidal absorption elements with a wider base of each trapezoidal
absorption element facing the image display side of the filter layer.

2. The rear-projection display device of claim 1, the screen further
comprising a lens sheet spaced from the filter layer, the lens sheet
being formed from a rigid sheet of material and having a first side
comprising a Fresnel lens to direct light to the filter layer and a
second side coated with an anti-reflective layer.

3. The rear-projection display device of claim 1, wherein the screen
further comprises: a rigid mechanical strength layer having a first side
and a second side; a Fresnel lens bonded to the first side of the rigid
mechanical strength layer; and an anti-reflective layer disposed on the
second side of the rigid mechanical strength layer.

4. The rear-projection display device of claim 3, wherein the filter
layer further comprises a planar surface that faces the Fresnel lens.

5. The rear-projection display device of claim 1, wherein each of the
trapezoidal absorption elements is configured to have a higher
transmittance of one or more wavelengths of infrared light than of one or
more wavelengths of visible light.

6. The rear-projection display device of claim 1, the screen further
comprising a light diffuser configured to diffuse light received from the
filter layer.

7. The rear-projection display device of claim 6, the screen further
comprising a transparent durability layer disposed on a light emission
side of the light diffuser to resist contact damage to the screen.

8. The rear-projection display device of claim 1, wherein the screen
further comprises a touch sensor.

9. The rear-projection display device of claim 8, further comprising: an
infrared light source configured to illuminate the screen with infrared
light; and an infrared image capture device configured to capture an
image of the screen at one or more infrared wavelengths emitted by the
infrared light source.

10. The rear-projection display device of claim 1, further comprising an
optical wedge configured to receive projected light from the projector
and transmit projected light to the screen.

11. A display screen, comprising: a lens sheet having a first side
configured as a Fresnel lens and a second side coated with an
anti-reflective layer; and a filter layer positioned to receive projected
light exiting the lens sheet, the filter layer comprising a light
reception side spaced from the lens sheet, and a plurality of
transmissive elements and a plurality of absorption elements, each of the
absorption elements being configured to have a higher transmittance of
one or more wavelengths of infrared light than of one or more wavelengths
of visible light.

13. The display screen of claim 11, wherein the plurality of absorption
elements and the plurality of transmissive elements comprise a plurality
of trapezoidal absorption elements interspersed with a plurality of
trapezoidal transmissive elements.

14. The display screen of claim 13, wherein a wider base of each of the
plurality of trapezoidal transmissive elements faces the light reception
side of the filter layer and forms at least a portion of a planar surface
of the light reception side of the filter layer.

15. The display screen of claim 11, the display screen further
comprising: an image display side of the filter layer located opposite to
the light reception side of the filter layer; a light diffuser for
diffusing light received from the filter layer bonded to the image
display side of the filter layer on a first side of the light diffuser;
and a transparent durability layer disposed on the light diffuser.

16. A horizontally-oriented rear-projection display system, comprising: a
projector configured to project light; and a display screen configured to
display an image projected by the projector, the display screen
comprising a mechanical strength layer having a first side and a second
side opposing the first side, the first side coated with an
anti-reflective layer; a Fresnel lens disposed on the second side of the
mechanical strength layer; a filter layer spaced from the Fresnel lens
and configured to receive light from the Fresnel lens, the filter layer
comprising a light reception side positioned to receive projected light
exiting the Fresnel lens, an image display side located opposite the
light reception side of the filter layer, an array of trapezoidal
transmissive elements arranged between the light reception side and the
image display side such that a wider base of each transmissive element
faces the light reception side of the filter layer, and an array of
trapezoidal absorption elements arranged between the light reception side
and the image display side such that a wider base of each absorption
element faces the image display side of the filter layer, each absorption
element having a higher absorbance than transmittance of one or more
visible wavelengths and a higher transmittance than absorbance of one or
more infrared wavelengths; and a light diffuser configured to diffuse
projected light received from the filter layer.

17. The horizontally-oriented rear-projection display system of claim 16,
further comprising an optical wedge configured to transmit projected
light from the projector to the display screen.

18. The horizontally-oriented rear-projection display system of claim 16,
wherein the display screen further comprises a touch sensor.

19. The horizontally-oriented rear-projection display system of claim 18,
further comprising: an infrared light source configured to illuminate the
display screen with infrared light; and an infrared image capture device
configured to capture an image of the display screen at one or more
infrared wavelengths emitted by the infrared light source.

20. The horizontally-oriented rear-projection display system of claim 16,
wherein the wider bases of the trapezoidal transmissive elements form at
least a portion of a planar surface of the light reception side of the
filter layer.

Description:

BACKGROUND

[0001] Rear-projection display systems may be of many different sizes and
configurations, and may vary according to any number of factors. Examples
of such factors include, but are not limited to, display screen
orientation, intended user viewing angle, optical system used for
projection, angle of incidence of light projected onto the display
screen, etc.

[0002] Depending upon the optics used to deliver a projected image to a
rear projection screen, ghost images may interfere with a viewing
experience. A ghost image appears on the display screen as an offset
replica of the projected image. A ghost image may be formed, for example,
when a projected image ray encounters an interface between media having
differing refractive indices. At such an interface, one portion of the
image ray may be refracted while another portion is reflected. The
reflected portion, or the ghost ray, may reflect off other surfaces
within the projection system and thereby appear on the display screen.

SUMMARY

[0003] Accordingly, various embodiments are disclosed herein that relate
to rear-projection image display. For example, one disclosed embodiment
provides a rear-projection display system comprising a projector for
projecting an image and a screen configured to display the image. The
screen comprises a filter layer having a light reception side and an
image display side. The filter layer includes an array of trapezoidal
transmissive elements and an array of trapezoidal absorption elements,
where a wider base of each of the trapezoidal transmissive elements faces
the light reception side of the filter layer, and where a wider base of
each of the trapezoidal absorption elements faces the image display side
of the filer layer.

[0004] This Summary is provided to introduce a selection of concepts in a
simplified form that are further described below in the Detailed
Description. This Summary is not intended to identify key features or
essential features of the claimed subject matter, nor is it intended to
be used to limit the scope of the claimed subject matter. Furthermore,
the claimed subject matter is not limited to implementations that solve
any or all disadvantages noted in any part of this disclosure.

[0011] As mentioned above, a rear-projection display may be of many
different sizes and configurations. For example, in some embodiments, a
rear-projection display system may take the form of a surface computing
system comprising a horizontally-oriented display screen configured to
display images to one or more users seated or standing around the display
screen. The surface computing device also may be configured to receive
touch inputs made on the display screen.

[0012] Depending upon the use environment, the display screens of such
surface computing devices may be sizeable, and therefore may be subject
to deformation due to gravity, users touching, leaning on or placing
drinks and/or other objects on the screen, and other factors not
ordinarily encountered by vertically-oriented rear projection display
screens. Further, a horizontally-oriented display screen also may have
other use constraints not ordinarily present for vertically-oriented
display screens. For example, because viewers of a horizontal display
screen may sit around the screen, the viewers may view the screen from
the side, rather than from the front. Therefore, it may be desirable to
direct a greater intensity of light toward the sides of the display
screen. Further, the optical systems used to deliver an image to the
display screen may produce ghost images with different characteristics
than those produced in a vertically-oriented rear projection system.

[0013] Therefore, embodiments of rear-projection display screens are
presented herein that may help to resist mechanical deformation, reduce
ghost image presentation, and distribute light intensity for a
horizontally-oriented rear projection display system such as a surface
computing device. While disclosed herein in the context of a
horizontally-oriented rear projection display system, it will be
understood that the embodiments described herein may be used in any other
suitable use environment, including, but not limited to,
vertically-oriented displays and displays having other suitable
orientations.

[0014]FIG. 1 shows an example embodiment of a rear-projection display
system 100 comprising an optical wedge 102 configured to deliver light
projected by projector 104 to a display screen 106 via total internal
reflection. The depicted optical wedge 102 comprises an internal
reflector 108 configured to form a folded optical path within the optical
wedge 102, such that the entire surface of the optical wedge 102 may be
used for image projection. Rear-projection display system 100 further
comprises a controller 110 configured to control the display of an image
via projector 104.

[0015] Rear-projection display system 100 further comprises a vision-based
touch-detection system configured to enable the detection of multiple
temporally overlapping touch inputs. In the embodiment shown in FIG. 1,
the vision-based touch detection system comprises an infrared light
source configured to illuminate the display screen 106 with infrared
light, and one or more image capture devices 112 configured to capture an
image of a backside of display screen 106 via infrared light reflected
from an object on display screen 106 into optical wedge 102. It will be
appreciated that, in some embodiments, the image capture devices may be
configured to capture an image of a frontside of the display screen based
on one or more focusing characteristics of the vision-based touch
detection system.

[0016] Any suitable light source may be used to illuminate the display
screen with infrared light. For example, in the depicted embodiment, a
plurality of infrared light-emitting diodes 116 may be arranged along one
or more edges of the display screen to inject infrared light into the
display screen. Additionally or alternatively, some embodiments may
incorporate a light source to provide an infrared backlight for
illuminating the display screen.

[0017] The light injected into the display screen may leak out of the
display screen, thereby allowing the light to be reflected into the
optical wedge 102 by any objects on the display surface 114. While
disclosed herein in the context of a horizontally-oriented display
system, it will be understood that an optical wedge also may be used to
deliver a projected image to a display screen having any other suitable
orientation. Further, it will be understood that the display screen
embodiments disclosed herein may be used in any other suitable use
environment.

[0018] The optical system of rear-projection display system 100 includes
various interfaces between materials of differing refractive indices
(e.g. wedge/air interfaces, interfaces between any cladding layers
disposed on the wedge, etc.) that may cause some light to be reflected at
such interfaces. This reflected light may then reflect from other
interfaces in the system back toward the display screen, thereby leading
to ghost images. Further, as light exits the optical wedge 102 of
rear-projection display system 100 at the critical angle for total
internal reflection, such light arrives at display screen 106 at a
relatively high angle of incidence relative to the display screen normal.
This also may cause issues with ghost images. Therefore, display screen
106 may be configured to block such ghost images. FIG. 2 illustrates an
embodiment of display screen 106 in more detail, and illustrates the path
taken through display screen by an example ray "A" of light projected by
projector 104.

[0019] Display screen 106 includes a filter layer 202 for filtering
undesired light, such as ambient light and ghost images; a lens sheet 204
for redirecting light received from the optical wedge 102 (or other
suitable light delivery system) toward a direction normal to a viewing
surface of display screen 106; and a light diffuser 206 for diffusing
light received from the filter layer 202. It will be appreciated that the
sizes of the various parts depicted in FIG. 2 are neither to scale nor
intended to represent any size relationships among those parts, but
instead are sized to clarify the arrangements and the locations of the
depicted parts.

[0020] Filter layer 202 includes light reception side 210 and an opposing
image display side 212. Image display side 212 is positioned to face
display surface 208 of display screen 106, while light reception side 210
is positioned to receive projected light from lens sheet 204. Filter
layer 202 also includes an array of trapezoidal absorption elements 214
interspersed with an array of trapezoidal transmissive elements 216 to
transmit projected light to display surface 208 while filtering ghost
images from the light projected to display surface 208.

[0021] Filter layer 202 acts to filter ambient light incident at display
surface 208 from the projection system that might otherwise lead to
reflection of the ambient light back to display surface 208 with an
accompanying loss in contrast. Each transmissive element of the array of
trapezoidal transmissive elements 216 has a wider base 218 facing light
reception side 210 of filter layer 202 and a narrower base 220 facing
image display side 212 of filter layer 202.

[0022] Trapezoidal transmissive elements 216 are configured to have a
higher transmittance than absorbance of one or more visible wavelengths
of light. In contrast, trapezoidal absorption elements 214 are configured
to have a higher absorbance than transmittance of one or more visible
wavelengths of light to absorb ambient light incident at display surface
208 and to absorb ghost images formed elsewhere in the projection system.
Each absorptive element of the array of trapezoidal absorption elements
214 has a wider base 222 facing image display side 212 of filter layer
202 and a narrower base 224 facing light reception side 210 of filter
layer 202.

[0023] Trapezoidal absorption elements 214 further may be configured to
have a higher transmittance of one or more wavelengths of infrared light
than of one or more wavelengths of visible light. For example, if light
source 116 is configured to produce infrared light, the infrared light
produced may be reflected by objects touching display surface 208 so that
display screen 106 is sensitive to a user touch, to an object placed on
display surface 208, etc. Thus, if trapezoidal absorption elements 214
have a higher transmittance of one or more wavelengths of infrared light
than of one or more wavelengths of visible light, trapezoidal absorption
elements will transmit a greater quantity of reflected infrared light for
capture by image capture device 112 while absorbing one or more
wavelengths of visible light, which may reduce the occurrence of ghost
images formed by reflected ambient light. Further, in some embodiments,
the trapezoidal absorption elements may be configured to have a higher
transmittance than absorbance of one or more wavelengths of infrared
light, providing a greater transmission efficiency of infrared light.

[0024] Trapezoidal absorption elements 214 may have any suitable
structure. For example, the trapezoidal absorption elements 214 may be
formed from or otherwise include an ink, dye or pigment that absorbs
light in the visible spectrum while transmitting light in the infrared
spectrum. The ink, dye or pigment may be incorporated into at least a
portion of each absorptive element of the array of trapezoidal absorption
elements 214; may be printed, coated, or adhered to either wider base 222
or narrower base 224 of each absorptive element of the array of
trapezoidal absorption elements 214; or may be incorporated into filter
layer 202 in any other suitable manner. In other embodiments, the
trapezoidal absorption elements may comprise a multilayer dielectric
filter, or any other suitable filtering mechanism than an absorbing ink,
dye or pigment.

[0025] The array of trapezoidal absorption elements 214 and the array of
trapezoidal transmissive elements 216 are arranged as a one-dimensional
(1D) array in FIG. 2. It will be appreciated that the array of
trapezoidal absorption elements may be in any suitable arrangement. For
example, in some embodiments where projected light is close to
telecentric and where ghost image generation occurs in more than one
dimension, a two-dimensional (2D) array of cone-shaped trapezoidal
absorption elements may be employed.

[0026] As mentioned above, FIG. 2 shows lens sheet 204 being spaced from
filter layer 202. Lens sheet 204 comprises a 2D Fresnel lens 226 for
redirecting light received from the projector toward a direction normal
to the surface of the display screen 106. Some embodiments of the display
screen may use a 1D turning film. For example, an embodiment used with an
optical wedge may include a linear or a nearly-linear turning film in use
cases where the projected light is nearly telecentric.

[0027] In the depicted embodiment, lens sheet 204 also comprises a rigid
mechanical strength layer 228 having a first side 230 and a second side
232. Fresnel lens 226 is positioned to receive projected light from the
second side of rigid mechanical strength layer 228 and to transmit the
projected light received to light reception side 210 of filter layer 202.
The Fresnel lens 226 may be connected to rigid mechanical strength layer
228 in any suitable manner. For example, the Fresnel lens 226 may be
bonded, fused, glued, etc. to rigid mechanical strength layer 228.

[0028] Rigid mechanical strength layer 228 comprises a mechanically rigid
material, providing mechanical support for display screen 106 to resist
screen bowing or sagging from user touches to display surface 208, from
objects placed on display surface 208, from the weight of display screen
106, etc. This may help to prevent damage to display screen 106 from such
factors, and also may help to preserve image quality, which may suffer if
display screen 106 deforms.

[0029] In some rear-projection display screens without such a mechanical
strength layer, the back surface (i.e. the surface that faces away from a
viewer) of a Fresnel lens sheet is roughened to avoid reflections that
could lead to ghosting, as well as avoiding aliasing and/or Moire effects
occurring between a projection image pixel pitch and a facet pitch of the
Fresnel lens. However, the presence of the mechanical strength layer 228
increases a distance between such a roughened surface and the filter
layer 202. Where the surface of the mechanical strength layer is
roughened, the diffusion of light caused by the roughened surface may
result in a portion of the projected light falling onto transmissive
absorption elements 214 in filter layer 202. This may result in reduced
light transmission to display surface 208, display of a blurry image at
display surface 208, problems with vision-based touch detection, etc.

[0030] Therefore, in some embodiments, second side 232 of rigid mechanical
strength layer 228 may be smooth, rather than roughened, to reduce
diffusion of the projected image onto the trapezoidal absorption elements
214. Further, an anti-reflective layer 234 may be disposed on second side
232 of rigid mechanical strength layer 228 to combat ghost images that
otherwise may be caused by reflection from the smooth surface of rigid
mechanical strength layer 228. Anti-reflective layer 234 may comprise any
suitable material or materials. For example, in some embodiments, the
anti-reflective layer 234 may comprise a multi-layer dielectric
anti-reflective structure.

[0031] As discussed above, light reception side 210 of filter layer 202 is
positioned to receive projected light exiting Fresnel lens 226, so that
ambient light and ghost images are filtered from the projected images. A
representative portion 300 of an embodiment of a Fresnel lens from lens
sheet 204 is shown in FIG. 3. Image ray A, shown entering base 302 of
Fresnel lens portion 300, refracts in the lens before exiting at facet
304 toward filter layer 202. Two ghost image rays that may arise from the
optical wedge 102 depicted in FIG. 1 are also shown in FIG. 3. One ray is
referred to as "low-angle ghost ray" and the other is referred to as
"high-angle ghost ray" based upon the angles relative to the display
screen normal at which the ghost rays exit the Fresnel facet. Low-angle
ghost image ray G1 enters base 302 at the same entry point as image ray
A, but at a different entry angle. Thus, low-angle ghost ray G1 is
internally reflected at facet 306 before being emitted at facet 304.

[0033] However, such a lenticular lens arrangement may be unsuitable for
addressing high-angle ghost image rays. Referring to FIG. 3, high-angle
ghost image ray G2 enters at a position on base 302 offset from the entry
point of low-angle ghost image ray G1 and image ray A. High-angle ghost
image ray G2 is internally-reflected at facet 304 before being emitted at
facet 306. In light of the angle at which ray G2 is refracted by the
Fresnel facet, the ray may pass between the absorbing stripes of a
lenticular-type filter. Thus, high-angle ghost image ray G2 may appear on
a display surface of a display screen.

[0034]FIG. 4 shows a graphical comparison of angular-dependent light
transmission from a display screen comprising a lenticular array with the
embodiment of FIG. 2. Lenticular lens transmission curve L exhibits a
low-angle main lobe transmission band 402 corresponding to image ray A
and a high-angle transmission band 404 corresponding to high-angle ghost
ray G2. In contrast, trapezoidal lens transmission curve T only exhibits
a low-angle transmission band 406 corresponding to image ray A. Thus, it
will be appreciated that a filter layer employing an array of trapezoidal
transmissive elements may be more suited to reducing ghost images
transmitted to a display surface than one utilizing a lenticular lens
arrangement.

[0035] Display screen 106 may be subject to forces during ordinary use
that bow the filter layer 202 toward the Fresnel lens 226. For example,
where the display screen 106 is used as a screen for a
horizontally-disposed surface computing device, users may push against
the screen with excessive pressure when making touch inputs, when resting
elbows on the screen, etc. Where a one-dimensional lenticular array (not
shown) is used as a filter, the "bumps" of the lenticular array may be
positioned sufficiently close to the facets of the Fresnel lens 226 that
the facets may scratch the lenticular array when excessive pressure is
pushed against the display screen. However, the use of the trapezoidal
array of filter layer 202 may help to avoid such problems. This is
because the wider bases of trapezoidal transmissive elements 216 and the
narrower bases of the trapezoidal absorption elements 214 provide at
least a portion of a planar surface 236 that faces Fresnel lens 226, and
thereby may increase a closest distance between the filter layer 202 and
Fresnel lens 226 compared to the use of a rear-projection lenticular
array. Moreover, a reduction in damage to facets of the Fresnel lens 226
may be realized by increasing a contact area between facets of the
Fresnel lens 226 and the planar surface 236 during a contact event
between the two structures. It will be understood that other embodiments
may utilize such a lenticular array.

[0036] Display screen 106 also comprises light diffuser 206 for diffusing
light received from filter layer 202 and spreading light in a viewing
direction from light emission side 240 of light diffuser 206. In a
horizontally-oriented rear-projection display system, light diffuser 206
may be a low-gain diffuser, configured to produce a Lambertian or similar
low-gain distribution of light, thereby facilitating viewing of an image
on the screen from the screen sides, and also not directing excessive
optical power along the screen normal, where it is less likely to be
viewed. Light diffuser 206 may further be configured to have a matte
finish to reduce specular reflection of ambient light from display
surface 208. Alternatively, light diffuser 206 may be configured to have
a glossy finish to provide an increased contrast ratio or to alter a
color intensity of the projected image.

[0037] Light diffuser 206 may be bonded to image display side 212 of
filter layer 202 on a first side of light diffuser 206. Display screen
106 may further comprise a transparent durability layer 238 disposed on
light emission side 240 of light diffuser 206 to resist contact damage to
display screen 106. The transparent durability layer 238 may help to
resist scratches to the display surface 208 caused by a user's finger, a
stylus, or other object contacting the display surface 208. The
transparent durability layer may comprise any suitable material, and may
be formed on light diffuser 206 in any suitable manner. Examples of
suitable materials include, but are not limited to, suitably hard
transparent ceramic coatings, polymer coatings, etc.

[0038]FIG. 5 shows another example embodiment of a rear-projection
display system 500 that may utilize the display screen embodiments
described herein. Rear-projection display system comprises a projector
502 configured to project an image, and a display screen 504 configured
to display an image projected by projector 502. Projector 502 includes a
light source such as lamp 506, light-emitting diode (LED) array, etc, and
also includes an image source 508, such as a liquid crystal display
(LCD), digital micromirror device (DMD), etc., for producing an image. In
the embodiment of FIG. 5, one or more mirrors 510 are utilized to
increase an optical path length and image size of the image projected by
the projector 502, instead of an optical wedge 102, to provide image
conjugates between the image source 508 and the projected image of the
image source 508 at or near the display surface 520. Rear projection
display system 500 further comprises a controller 512 configured to
control the display of an image via the projector.

[0039] The rear-projection display device 500 also comprises an image
capture device 524 configured to capture an image of the backside of
display screen 504. Image capture device 524 provides an image to
electronic controller 512 for the detection of an object 522 on the
display screen. It will be appreciated that, in some embodiments, the
image capture device may be configured to capture an image of a frontside
of the display screen based on one or more focusing characteristics of
the display system.

[0040] An infrared light source 526 may be used to illuminate the backside
of the display screen with infrared light to facilitate vision-based
touch detection. In other embodiments, a visible light source may be
used. However, the use of infrared light, as opposed to visible light,
for vision-based touch detection may help avoid washing out of the
projected image.

[0041] Other embodiments of rear-projection display system 500 may utilize
other approaches to detect user touches or objects at display surface 520
of display screen 504. For example, display surface 520 may include
capacitive or resistive touch sensor mechanisms (not illustrated)
configured to communicate with electronic controller 512, an external
computing device, a network, etc.

[0042]FIG. 6 illustrates another embodiment of a lens sheet in which the
Fresnel lens and mechanical strength layer comprise a single layer of
material. As such, lens sheet 600 is formed from a rigid sheet of
material 602, and comprises a Fresnel lens 604 molded, embossed, or
otherwise directly formed thereon to direct projected light to filter
layer 202. Lens sheet 600 further comprises a second side coated with an
anti-reflective layer 606 to help prevent the generation of ghost images
arising from the reflection of a projected image from the second side of
the lens sheet. As elsewhere, it will be appreciated that the sizes of
the various parts depicted in lens sheet 600 are neither to scale nor
intended to represent any size relationships among those parts, but
instead are sized to clarify the arrangements and locations of the parts.

[0043] It will be appreciated that, for some embodiments of
rear-projection systems where incoming light has a high incidence angle
with respect to a surface normal of the lens sheet, a portion of the
light may be reflected from the lens sheet, causing ghost images to form.
To address this in part, some embodiments may include a total internal
reflection (TIR) Fresnel lens or a combination Fresnel--TIR Fresnel
transition lens disposed adjacent the second side of the lens sheet in
place of and/or in addition to a Fresnel lens disposed on the first side
of the lens sheet. In such situations, the anti-reflective layer
described above may be modified or omitted according to the embodiment of
the display system.

[0044] While disclosed herein in the context of specific example
embodiments, it will be appreciated that the display screen embodiments
described herein are exemplary in nature, and that these specific
embodiments or examples are not to be considered in a limiting sense,
because numerous variations are possible. The subject matter of the
present disclosure includes all novel and nonobvious combinations and
subcombinations of the various processes, systems and configurations, and
other features, functions, acts, and/or properties disclosed herein, as
well as any and all equivalents thereof.